E10001 – Liquid Rocket Engines (J-2X, RS-25, general)

J-2X Progress: Current Status, The End of 2012

Once upon a time, not that long ago, people used to communicate by what were known as “letters.” These were written documents. Yes, actual hardcopy, paper items. And they were often transcribed by hand or, sometimes, generated on what was known as a “typewriter,” which was basically a manual, analog printer with no I/O port beyond direct keypad entry. These “letters” were sent to their intended recipients using a small denomination currency with an adhesive backing that is recognized for exchange by only one quasi-governmental agency.

I know that some of you may have doubts that people communicated with each other in primitive ways prior to email and text messages, but witness the cultural clues from the 1961 song illustrated above.

It was always believed that the toughest letter to receive was the dreaded “Dear John” letter (as in, “Dear John, I’ve fallen in love with someone else…”). However, I think t’at the hardest letter to write is the “it’s been awhile” letter. This one starts, “Well, it’s been awhile since I’ve written. Sorry.” This blog article is just like one of those letters. It’s been awhile since I’ve written one of these articles and I’m sorry about that. I could give you a big long list of all the really, really serious stuff that I’ve been doing instead, but that’s just a bunch of feeble excuses so I’ll keep them to myself. Instead, I’ll just get down to business and give you a status report on the J-2X development effort.

Engine #1 (E10001) Testing is Complete!
Over fourteen months and across the span of twenty-one tests, more than 2,700 seconds of engine run time was accumulated and recorded, including nearly 1,700 seconds of hot fire with an instrumented nozzle extension. With this engine we achieved stable 100% power level operation by the fourth test and full mission duration by the eighth test. While we don’t have any official statistics on the issue, most folks around here believe that we accomplished those milestones faster than has ever been done on a newly developed engine. We learned how to calibrate the engine and the sensitivities that the engine has to different calibration settings, i.e., orifice sizes and valve positions. We were able to estimate performance parameters for the full-configuration of the engine at vacuum conditions and the calculations suggest strongly that all requirements are met by this design and met with substantial margin. This is significant considering that we’ve long considered our performance goals to be pretty aggressive. Well, our little-engine-that-could showed us that it did just fine with those goals, thank you very much.

One of the truly unique and successful aspects of the E10001 testing was the testing of a nozzle extension. This component is a key feature that allows J-2X performance to far exceed that of the J-2 engine from the Apollo Program era. While it is true that we cannot test the full-length nozzle extension without a test stand that actively simulates altitude conditions, we did test a highly instrumented “stub” version that allowed us to characterize the thermal environments to which the nozzle is exposed during engine hot fire and it demonstrated the effectiveness and durability of the emissivity coating that was used. This stub-nozzle configuration is actually the current baseline for the in-development Space Launch System vehicle upper stage.

Another key success for E10001 was the demonstration of both primary and secondary power levels with starts and shutdowns from each power level and with smooth in-run transitions back and forth between them. That smoothness was thanks, in part, to demonstrating our understanding of the control of the engine. From the very first test it was clear that we understood pretty well how to control the engine in terms of proper control orifices for the various operating conditions. What we did not entirely understand — in other words the fine-tuning details — we successfully learned via trial-and-error throughout the E10001 test series. All of this learning has been fed back into further anchoring our analytical tools and models so that we can move forward with J-2X development with a great deal of confidence.

Okay, so that’s a brief description of just some of the good stuff. We had lots and lots of good stuff with the E10001 testing, far more than just that I’ve discussed here (see previous blog articles). The somewhat unfortunate part was the way in which the E10001 test series came to an end. On test A2J021, we had a disconnection between the intent for test and the detailed planning that led to the actual hardware configuration we ran for the test. That disconnection led to an ill-fated situation. Let me explain…

The J-2X gas generator has ports into which solid propellant igniters are installed. These igniters are like really high-powered Estes® rocket motors that light off when supplied with a high-energy electrical pulse. The flame from the igniter lights the fire of the hydrogen-oxygen mixture during the engine start sequence. It’s essentially the kindling for the fire of mainstage operation. The igniters perform this function at a very specific time during this sequence. If you try to light the fire too early, then you may not have enough propellant available in a combustible mixture so you get a sputtering fire. If you try to light too late, then you may have too much propellant built up such that rather than getting a good fire, you get an explosion instead. But here’s a key fact: You have to plug them in or they don’t work.

Have you ever stuck bread in the toaster, pushed down the plunger, gone off to make the coffee, and come back only to find that your darn toaster is broken? You curse a little because you’re already late for work and this is the last darn thing you need. You would think that somebody somewhere could make a toaster that lasts more than six months or a year or whatever. For goodness sake! We put a man on the moon and yet we can’t … oh, wait … um … ooops, it’s not plugged in. My bad.

In a nutshell, that’s what happened on test A2J021. The electronic ignition system sent the necessary pulse, but because of the uniqueness of our testing configuration as opposed to our flight configuration the wires carrying the pulse weren’t hooked up to the little solid propellant igniters in the gas generator. In the picture below you can see the external indication that something was not entirely good immediately after the test. The internal damage was more extensive to both the gas generator and the fuel turbopump turbine.

Many years ago, I met an elderly engineer who was still on the job well into his 80’s because he loved his work. His entire career had been dedicated to testing. He’d actually been there, out in the desert, in the 1940’s testing our very earliest rockets as part of the Hermes Project. One day, they had a mini disaster on the launch pad. He told me that the rocket basically just blew up where it sat. Boom and then a mess. And, it was his job to assemble the test report. Being a conscientious, ambitious, young engineer, he recorded the facts and offered a narrative abstract and extensive, annotated introduction that categorized the test as, well, a failure. Not long after submitting his report, one of the senior German engineers in the camp came into his office, put the test report down on the desk, and said that the tone of the report was entirely wrong. He said, “Every test report should begin with: ‘This test was a success because…'” The purpose of testing is to gather data and learn. If you learn something, then your test was, by definition, a success on some level. I’ve tried very hard to remember this very important bit of wisdom.

So, A2J021 was a success because we learned that we had some deficiencies in our pre-test checkout procedures. It was a success because it was an extraordinary stress test on the gas generator system. No, it didn’t recover and function properly, but neither did the engine come apart. While that might seem like a minor detail, when you’re hundred miles from the surface of the earth, you would much rather have a situation where an abort is possible than a failure that could result in collateral vehicle damage and make safe abort impossible. We have a stout design. Good. Also, this test failure was due to a unique ground test configuration. In flight, it’s not really plausible just because we would never fly in this configuration.

So, E10001 completed its test program with a bang. Kinda, sorta literally. But it was nearly the end of its design life anyway, so we didn’t lose too many test opportunities, and, as I said, even with test A2J021 the way it happened we learned a great deal. Overall, the E10001 test series was an outrageous success. Rocketdyne, the J-2X contractor, ought to be darn proud and so should the outstanding assembly and test crews at the NASA Stennis Space Center and our data analysts here at the NASA Marshall Space Flight Center. Bravo guys! Go J-2X!

Power-Pack Assembly 2 (PPA-2) Testing is Complete!
Over ten months and across the span of thirteen tests, nearly 6,200 seconds of engine run time was accumulated and recorded on the J-2X Power Pack Assembly 2. That’s over 100 minutes of hot fire. Three of the tests were over 20 minutes long (plus one that clocked in at 19 minutes) and these represent the longest tests ever conducted at the NASA Stennis Space Center A-complex. But more than just length, it was the extraordinary complexity of the test profiles that truly sets the PPA-2 testing apart.

Because PPA-2 was not a full engine with the constraints imposed by the need to feed a stable main combustion chamber, and because we used electro-mechanical actuators on the engine-side valves and hydraulic actuators on the facility side valves, we could push the PPA-2 turbomachinery across broad ranges of operating conditions. These ranges represented extremes in boundary conditions and extremes in engine conditions and performance. On several occasions we intentionally searched out conditions that would result in a test cut just so that we could better understand our margins. As the saying goes: It’s only when you go too far do you truly learn just how far you can go. We successfully (and safely) applied that adage several times. In short, we gathered enough information to keep the turbomachinery and rotordynamics folks blissfully buried in data for months and months to come.

On an interesting and instructive side note, the PPA-2 testing also showed us that we needed to redesign a seal internal to the hydrogen turbopump. In the oxygen turbopump, you have an actively purged seal between the turbine side and the pump side. After all, during operation you have hydrogen-rich hot gas pushing through the turbine side and liquid oxygen going through the pump side. You obviously don’t want them to mix or the result could be catastrophic. That’s why we have a purged seal. But for the hydrogen turbopump you don’t have such an issue. During operation, at worst should the two sides mix you could get some leakage of hydrogen from the pump side into the turbine side that is already hydrogen rich. In order to maintain machine efficiency, you don’t want too much leakage, but a little is not catastrophic (and can be used constructively to cool the bearings). What could be dangerous at the vehicle level, however, is if you have too much hydrogen floating around prior to liftoff. This is especially true for an upper-stage engine like J-2X that’s typically sitting within an enclosed space until stage separation during the mission. You could have the engine sitting on the pad for hours chilling down and filling the cryogenic systems and you don’t want gobs and gobs of hydrogen leaking through the turbopump since any leakage ends up within the closed vehicle compartment housing the engine. That’s just asking for an explosion and a bad day.

To avoid this, within the J-2X hydrogen turbopump we have what is called a lift-off seal. And, as the name applies, it’s a seal that actively lifts off when we’re ready to run the engine. When the engine is just sitting there chilling down, not running, with liquid hydrogen filling the pump end of the hydrogen turbopump, the seal is, well, sealed. Then, when we’re ready to go, it unseals and allows the turbopump to operate nominally.

During the PPA-2 test series we found that we formed a small material failure within the actuation pieces for our lift-off seal. Then, upon analysis of the test data and a reassessment of the design, we figured out what was most likely the cause and Rocketdyne proposed a redesign to mitigate the issue. Again, going back to that important piece of wisdom: This testing was a success because, in part, we learned that we needed a slight redesign of the lift-off seal. That’s the whole purpose of development testing! Everything always looks great when it’s just in blueprints. It’s not until you hit the test stand do you truly learn what’s good and what need to be reconsidered. In the end, this sort of rigor and perseverance is what gives you a final product that you feel good about putting in a vehicle carrying humans in space. And that, truly, is what it’s all about.

As with E10001, the PPA-2 test series was simply an outrageous success. Rocketdyne should be proud and so should the outstanding assembly and test crews at the NASA Stennis Space Center and the data analysts at the NASA Marshall Space Flight Center. Bravo guys! Go J-2X!

Engine #2 (E10002) Assembly is Underway
Our next star on the horizon is J-2X development Engine 10002. It is being assembled right now, as I’m typing this article. It is slated for assembly completion in January 2013 and it will be making lots of noise and very hot steam in the test stand soon after that. While our current plans are to first test E10002 in test stand A2, we will later be moving it to test stand A1. This, then, will be the first engine then to see both test stands. The more important reason for the A1 testing, however, is because that will give us the opportunity to hook up some big hydraulic actuators and gimbal the engine, i.e., make it rock and tilt as though it were being used to steer a vehicle. Now that will be some exciting video to post to the blog! I can’t wait.

Happy New Year!
So, this has been my “it’s been awhile” letter. Hopefully this will bring everyone up to speed with where we stand with J-2X development. In my next article, I will share with you some of what’s been keeping me from my J-2X article writing over the last several months. And, hopefully, it won’t be several months in the making. So, farewell for now and Happy New Year! On to 2013 and another great year full of J-2X successes. Go J-2X!

J-2X Progress: The Next Phase for E10001

In January, the Chinese people celebrated their traditional New Year and formally initiated the year of the Dragon. I was born in the year of the Dragon (it comes up every twelve years) and I started thinking about previous Dragon years and where I was when they occurred. My first year of the Dragon after my birth happened to be the 200th birthday of our great country and I was starting sixth grade. My second year of the Dragon was the year that I got married so that was kind of important to me on a personal level. My third year of the Dragon was the year that I started working for NASA after spending a decade working for defense and space industry contractors. It is interesting looking at one’s life in such a series of widely separated snapshots. Things move on.

The same is true for J-2X. Last year was momentous for our project. We assembled and tested our first development engine, E10001. We celebrated and received well-deserved (if I do say so myself) kudos and pats on the back. But now things move on and the life of our good friend E10001 enters its next phase. And the next phase for E10001 involves changes to its nozzle configuration. So, before I tell you specifically what we’re doing to E10001, we need to discuss how a supersonic nozzle works.

Below is a schematic of what, on a rocket engine, would be called the thrust chamber assembly or the main injector plus main combustion chamber plus the nozzle. Within the realm of compressible flow this is known as a convergent-divergent nozzle, or as a “de Laval nozzle” after a late 19th-century Swedish engineer, Gustaf de Laval, who pioneered using such shapes as part of steam engines […and you woke up this morning not realizing that you’d learn something historical today!]. How it works is simple. Fluid flows from high pressure at the head end on the left towards the low pressure at the exhaust on the right. In between, the flow area of the “pipe” in which the fluid flows is manipulated to accelerate the fluid. The most narrow point in the flow is called the throat. Fluid flow to the left, upstream, of the throat is subsonic, i.e., traveling at less than the speed of sound. If the ratio of “high” to “low” pressure at the two ends is large enough, then fluid flow to the right, downstream, of the throat is supersonic, i.e., traveling at greater than the speed of sound. Under such conditions, the velocity at the throat itself is exactly that of the speed of sound. In other words, the fluid is traveling at “Mach 1” at the throat [the term named for Ernst Mach, an Austrian scientist and philosopher also from the late 19th century]. Oh, and all of this only works if your “fluid” is compressible, or in other words a gas like air or, in a rocket, combustion products.

How and why this happens gets a little heavy on the thermodynamics, so please just trust me for now. But the really neato thing that Mr. De Laval learned when playing with convergent-divergent nozzles like this is that: (1) for subsonic flow, as the flow area gets smaller, the flow velocity goes up, (2) for supersonic flow, as the flow area gets larger, the flow velocity goes up. In other words, they act the opposite of each other. For a rocket, this is absolutely fantastic since the whole idea of a rocket is to fling stuff out the back end at very, very high velocity and this cool device accomplishes that with just a little bit of creative geometry.

Okay, with me so far?

Then, here’s another thing to think about regarding supersonic flow: You can’t shout upstream. Sound is nothing more than pressure waves traveling through a fluid. A gas has a characteristic speed at which pressure waves are conveyed within it. That, then, is the speed of sound. So, if the gas is traveling at greater than the speed of sound, then pressure waves cannot travel upstream. Think of it this way: imagine yourself to be a gas molecule. Normally, when traveling less than the speed of sound, you can receive signals from all directions. Your motion can be impacted by pressure waves both upstream and downstream of where you sit at any given time. However, now imagine that you are that gas molecule hurtling along in a supersonic flow. Now, because you’re traveling faster than the ability of pressure waves to get back upstream, you can have no idea what’s going on downstream. You’re flying along blindly.

Thus, the bottom line is that once the ratio of high and low pressures are sufficient to cause this situation of supersonic flow in the divergent portion of the nozzle (a term that we use is that the throat is “choked”), then the nozzle flow is the nozzle flow. In other words, it is largely independent of what happens beyond the exit plane. Largely, but not entirely. I’ll explain below. Hold on.

Next, we’re going to talk about the Bernoulli Equation [developed by an 18th-century father and son team of Swiss professors Johann and Daniel Bernoulli]. No, we’re not going to do any math. All that we have to do is understand the concept of the Bernoulli Equation and how it relates to the flow in the divergent portion of our nozzle. Here it is: Absent other factors, when fluid is accelerated, its pressure drops. You can think of this in terms of energy. Pressure is like stored energy, as in electrical energy in a battery. Velocity is active energy, as in electrical energy spinning a fan. Absent any other input or output, when you show more active energy (velocity), you then have less stored energy (pressure).

Just for fun, here are some pictures of the men I’ve mentioned so far. Oh, and I tossed in a friend of Daniel Bernoulli’s named Leonhard Euler. Anyone who knows anything about mathematics or fluid dynamics knows all about Mr. Euler. He was truly a genius on par with Sir Issac Newton. (BTW, I kinda like the white, powdered wig thing the Bernoulli guys had going there. Maybe I’ll adopt it myself…)

Back to the topic at hand. Where do we stand once we combine compressible fluid flow through the divergent portion of a de Laval nozzle, traveling at speed greater than Mach 1 (meaning that pressure waves cannot travel upstream), and with the application of the Bernoulli Equation and the effect on pressure? I will attempt to show you in a picture…

So, if I make my nozzle longer and longer and longer, with a larger and larger exit size, my exhausting gas goes faster and faster and faster. Again, that’s why rocket engines have big divergent nozzles. Ta-da! But, there are limits. There always are. Nothing is free.

The first limit is weight. As your nozzle gets bigger and bigger, your nozzle structure gets heavier and heavier. As some point, any gain in engine performance is offset by the loss of vehicle performance because your engine is too heavy to lift.

The second limit is due to what’s on the other side of the exit plane. What’s outside the nozzle is, well, the ambient environment. If you’re sitting at the NASA Kennedy Space Center in Florida, where we usually launch our rockets, the ambient conditions are known as “sea level” conditions, meaning that the atmospheric pressure averages about 14.7 pounds per square inch. On the other hand, if you’re floating around in space and in orbit around the earth, then your ambient conditions are, to a pretty good approximation, a vacuum, meaning 0.0 pounds per square inch pressure.

What happens if you’re that gas molecule hurtling along in the flow at supersonic velocity down the nozzle and then you’re suddenly flung into ambient conditions? Well, if you’re in the main part of the flow, not much. You eventually slow down through a series of oblique shocks external to the nozzle. As I said above, if you’re moving supersonically within the nozzle, then you’re not affected by what’s downstream. But what if you’re not in the main flow but instead along the wall? Here’s a secret: The flow along the wall is slower than the main, core flow. Indeed, exactly at the wall, in the limit, the velocity is zero. That changes things.

So, exactly at the wall, the velocity is zero, and just fractions of an inch into the flow the velocity is supersonic. This transition zone is known as the “boundary layer” and the fluid dynamics complexity here can be nearly mind boggling and it has to do with viscous friction between the fluid and the wall. But the important point is that there is a thin layer that is not supersonic. Below is a typical textbook-like representation of boundary layer flow.

Remember when I said that what happens beyond the exit plane largely doesn’t affect the fluid flow in the nozzle? The boundary layer is the exception. Because the flow here is subsonic, pressure conditions downstream can influence things upstream. And here is the source of the other limit on your nozzle size.

If the ambient pressure is much, much higher than the pressure of the nozzle flow, then this pressure can slow up the subsonic portion along the wall. If you slow it up enough, you can make the boundary layer thicker and thicker until it’s no longer just fractions of an inch thick. Having a thick boundary layer means that your nozzle is not flowing “full.” The flow can become “detached” from the wall and such a situation is inherently unstable. All around the nozzle, in local pockets, the boundary can grow and collapse and grow again causing localized pressure variations. Shock waves start bouncing around. Then the nozzle structure itself, usually not built very stiff so that it doesn’t weigh too much, starts to respond to these local pressure variations and shock waves and it wobbles and ripples and buckles. To put is more succinctly, if your nozzle expands the rocket exhaust flow too much for the ambient conditions, you have an “over-expanded” condition and this can literally tear the nozzle apart. Below is a picture that tells the story of the impact of ambient pressure on nozzle flow.

Now, finally, we’ll get back to J-2X E10001.

For all of the tests conducted to date, the nozzle that we’ve tested on E10001 has had an expansion ratio of 35 to 1, meaning that the area of the exit plane is thirty-five time larger than the area of the throat. With this kind of expansion ratio for this engine, the nozzle flow is not over expanded. The nozzle “flows full” at sea level conditions like those seen at the NASA Stennis Space Center (SSC) where we test the engines and all is good. But the J-2X is intended to be an upper stage engine in flight, meaning that when it fires during the mission, it will be at over 100,000 feet in the altitude where the ambient pressure is much less than sea level conditions. Because of that, we designed the engine to use a larger nozzle, get more performance from greater exit velocity, and not over expand the exhaust flow at THOSE conditions way up in the upper atmosphere, practically in space.

But then how do we test it? If we have a nozzle that flows full at altitude, but does not flow full (i.e., it’s over expanded) at sea level, then how do we perform a test showing that the nozzle works? We can’t exactly build a test stand at 100,000 feet in the sky. Instead, we make the test stand simulate these high-altitude conditions. Below is a picture of NASA SSC test stand A-2. What you see there in the middle, the big tube several stories tall surrounded by structures, is the passive diffuser.

The diffuser, combined with a clam-shell enclosure structure around the bottom portion of the engine, uses Bernoulli effects (see, they come into play again!) such that when the engine is firing, it does so into an ambient environment that “appears” to be like that at high altitude. By doing this, for the next phase of J-2X E10001 development, we will be able to do testing with a nozzle extended to an expansion ratio of 59 to 1. That is one step closer to the ultimate flight configuration for the J-2X as part of the exploration mission and therefore one step closer to fulfilling that mission. It takes a bit of explaining to understand why all this is necessary, but the bottom line truly is that we are getting closer and closer to our exploration goals.

So, enjoy come on along with us to celebrate the Year of the Dragon with the generation of lots of smoke and fire from the J-2X. It’s going to be fun. But first, maybe a few traditional Chinese New Year’s treats…

J-2X Doghouse: Okay, So We Ain't That Smart — Yet

Welcome back to the J-2X Doghouse. We’re going talk about some test results and test data, exactly what Data Dogs love most to do.

Back in the day — back before I had the carefully regulated, federally mandated, and strictly enforced lobotomy that allows people into the ranks of management — I was once an analyst. And, since it seems so long ago that it doesn’t sound like bragging anymore, I will admit that I was pretty good at it. I absolutely loved the process of using fundamental physics or empirical correlations for fluid dynamics, thermodynamics, and heat transfer all together to simulate in computer coding how things function in the real world. Whereas many people enter the field engineering because they like mechanical things or electronic things, there are some of us who relish the seeming purity of problem solving in abstraction.

Over the years, working on many diverse projects and building many diverse mathematical models to simulate many diverse systems, I came to the realization that my models always appeared most unassailable and brilliant when there was no test data against which to compare them. To put it bluntly, test data always proves that you simply ain’t as smart as you thought you were. But, that’s okay. If that wasn’t the case, then you wouldn’t bother to test. The whole point of testing to gather data and learn more.

With all due respect to the Serenity Prayer, this ought to be the analyst’s prayer relative to testing:

Grant me —
— the results to validate that which I do understand
— the data to explain that which I did not understand
— and the openness to accept that I can always understand better

That last line is critical. Ignoring data contrary to what your model output is a seductive, addictive, and dangerous path to follow. We don’t/won’t do that.

That brings us to the subject of test A2J003 of the J-2X development engine E10001. This was our first test to mainstage operation. The planned duration was to be seven seconds. On Tuesday 26 July, right around five in the afternoon, the test ran for 3.72 seconds and then shutdown. We did not accomplish the full duration. Why? Basically because we ain’t as smart as we thought we were. We had analytical models telling us that performance would be X, but the hardware knew better and decided on its own to perform to Y. Here is a cool video of the test:

J-2X Engine Test A2J003

A more detailed explanation of what happened is that the engine shutdown due to the measurement of a pressure too high in the main combustion chamber. The measurement crossed a pre-set “redline” and the test controller unit took the automatic (and autonomous) action of shutting down the engine in a safe and controlled manner. The high pressure in the main chamber was caused by higher than expected power coming out of the oxidizer pump. This, in turn, was due to more power being delivered to the turbine side than expected. It comes down to a fluid dynamics phenomenon (pressure drops) and what we have is not inherently bad, just different than expected. So, in essence, we used our models to predict that the pressure in the main chamber would be at a certain level — indicating a certain power level — but the different performance of the hardware resulted in pushing us away from our analytical prediction.

Here is the good part: We learned something. We learned that our model needs to be updated and we collected the data that will allow that to happen.

Here is another good part: We got enough data, despite the short duration, to recalibrate the engine for the next test thereby making it far more likely that we will hit our target. .

Here is yet another good part: We had a successful demonstration of the test controller redline system by safely shutting down the engine. The engine looks fine. The controller did exactly what it was supposed to do and protected the hardware. In fact, for these early tests we have the redlines clamped down pretty tight specifically to protect the hardware as we learn more about the engine..

And here is, finally, yet another good part: Other than the power applied to the oxidizer turbopump, most of our other predictions with regards to hardware performance appear to be awfully darn good. So, we’ve got a preliminary validation for much of our understanding of the engine. Indeed, this is a brand new engine and we have just accomplished mainstage operation in the second hot-fire test. That is truly unprecedented..

Here is the bad part: We have to spend a few minutes explaining to folks not directly involved that despite not achieving full duration, the test was in reality a total success.

If that, then, is the bad part, I can live with it. I can live with admitting that we ain’t as smart as we thought were. Why? Because now, after the test, we are indeed smarter. And we will continue to get smarter and smarter about the J-2X design until, one day, we will be smart enough to say that, yes, we understand this engine so well that it is safe enough to propel humans into space.

J-2X Progress: Road Trip, Baby!

It wasn’t too many years ago that there was this thing about asking sports heroes after winning the big game, “So, what’s next?” They would always dutifully answer “I’m going to Disney World!” I guess that that whole thing is passé since I’ve not heard it in awhile, so I am going offer an alternative. Maybe it’ll catch on and be the BIG THING this summer…

…or, well, maybe not.

But that is what happens next. Our little engine is pulled out of the air-conditioned confines of its assembly area and trucked across the NASA Stennis Space Center to its test stand. No more pleasantly cool and dry air for you, E10001. This is Mississippi in June. Thus, in order to make this trip out in the open like this on the back of the truck (don’t try this at home!), the engine has to be sealed up tight against the humidity (and bugs) hanging in the air. Anywhere where there is an opening, there is a cover, a closure, or a plug. From the lot at the assembly building in picture (1) below, down the road towards the engine testing area in pictures (2) and (3), and finally arriving at the lot behind test stand A-2 in picture (4). In picture (5), you can see that the truck backs in alongside the test stand for the next operation.

The next operation is to get the engine up into the test stand. Years ago, this test stand was built for testing the Apollo Program S-II stage (the second stage of the Saturn V vehicle that was powered by five J-2 engines). Back then, they basically picked up the whole stage (from a canal barge, not a flatbed truck) high into the air and lowered it down from above into the stand. When it was converted to be an engine-only test stand for Space Shuttle Main Engine testing in the early 1970’s, propellant tanks were added on top of the stand. So you can no longer lower the test article in from way up above. Rather, you lift it up about four or five stories and then pull it in laterally. This is the “engine deck,” the level where the engine will be installed into the stand. In the pictures below you can see the operation of pulling the engine off the transport truck and up to the engine deck level of test stand A-2.

After the engine is lifted to the correct height, it is brought laterally into the stand and set down on the “porch.” That’s what the folks on the test stand call it: the porch. The other day somebody (obviously from out of town) mistakenly referred to it as the “veranda.” We’ll have none of that fancy talk around here! The thing onto which the engine is set is the Engine Vertical Installer (EVI). This is a hydraulic lift table that will be used to raise the engine into place when it is to be bolted to the test stand. So, here is the sequence: you lift the engine up to the engine deck level, you pull it into the stand and set the engine down on the EVI sitting on the porch, then you slide the EVI horizontally into the heart of the test stand (the EVI is on rails for this purpose), you then raise the engine into the test position, bolt it in place, and then you slide the EVI back out of the way. Ta-da! Now you’ve installed an engine for test!

In the pictures below you can see the technicians positioning the engine onto the EVI on the porch. In the bottom picture of the set, you can see in the background to the left test stand A-3 still under construction and, to the right, test stand A-1 where, early next year, J-2X powerpack testing will be conducted.

So, our little baby engine is all grown up and ready to see the great big world from high up in the test stand. The next phase of our development program is now begun: the testing phase. After the engine is installed and the test stand is readied for hot fire, J-2X development engine E10001 will be used to demonstrate basic operations such as start, mainstage, and shutdown, to verify main chamber combustion stability, and to provide initial validation of numerous systems-level simulations and models.

Okay, somebody go carefully poke the Datadogs because soon we’re going to have genuine, full-up rocket engine test data from J-2X. And, as a final note, I offer an extra special tip of the hat to all of the folks at SSC (NASA, Pratt & Whitney, and support contractors) for doing an amazing job in terms of engine assembly and test stand readiness preparations. Don’t ever think that your extraordinary efforts go unrecognized or unappreciated. Bravo!